CA2100900A1

CA2100900A1 - Filter with triangular fingers

Info

Publication number: CA2100900A1
Application number: CA002100900A
Authority: CA
Inventors: Jean-Philippe Cottenceau; Gerard Chevillon
Original assignee: Celsa LG SA
Current assignee: B Braun Medical SAS
Priority date: 1992-08-07
Filing date: 1993-07-20
Publication date: 1994-02-08
Also published as: JPH06205799A; FR2694491B1; EP0582493B1; DE69312599D1; ES2104094T3; JP3479102B2; US5344427A; EP0582493A1; FR2694491A1; ATE155992T1; DE69312599T2

Abstract

ABSTRACT
A filter for placing, in a folded condition, into a part of the blood system, and unfolding to restrain blood clots, comprises a plurality of resilient fingers which can be unfolded and are provided at their free ends with centring and bearing runners. The fingers and the runners comprise flexible wires and are assembled in pairs of adjacent fingers joined at their ends by a wire part folded in the form of a hairpin.

Description

- 2l00~n FILTER WITH TRIANGULAR FINGERS
The invention relates to a filter for placing in the blood system, especially in the course of a vein, for retaining blood clots.
Filters of this type are described for example in US patent No. 4,688,553.
Generally, these filters are in the form of a small frustoconical basket which attaches to the interior of a vein downstream of the path which is to be filtered; generally the vena cava arriving at the heart. It is thus possible to stop any blood clots which may have been formed, before they enter the heart, reducing the risk of them causing embolisms.
Usually these filters are of two main types.
The first type comprises filters produced from metal wires assembled together by welding or crimping. These filters are small and flexible. Once bent, they are not bulky and are well-suited to insertion by routes which are difficult and have pronounced anatomical curvatures.
The second type comprises filters produced from plates generally enabling the filtering portion to be produced in one part which is cut out and shaped. These filters have a large bearing surface in contact with the vein, thus reducing trauma and eliminating the risks of perforation.
However, filters of these two types have various disadvantages.
With respect to the filters produced with wires, the flexibility of the wires causes two considerable defects:

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- firstly it prevents consistent bearing forces being applied to the vein wall, so the filter is thus not held well and can migrate;
- secondly, the wire is small; so the bearing surface in contact with the vein is restricted which can give rise to trauma and perforations.
Furthermore, there is a risk of the wires becoming tangled, particularly at the moment when the device is fitted, thus reducing the filtering capacity of the filters.
The filters produced from plates have a high degree of rigidity in their constricted fitting condition which renders them awkward to fit via routes which are initially sinuous.
Also, they are considerably bulky, owing to the surfaces, and do not enable very fine insertion devices to be used, which increases trauma at the point of puncture.
Furthermore, filters formed from a conical portion provided with filtering components are generally difficult to position correctly. Generally, in order to introduce a filter of this type into the blood vessel, it is pushed there by way of a tube 2~ known as a catheter which passes through the said blood vessel and is of lesser diameter than the latter. When the filter arrives at the end of the insertion tube, it is released into the vessel and the expansion of its fingers, frequently provided with hooks, anchors it in place.
In practice a "release" of this type is very awkward to control and a certain number of cases have ensued wherein the basket-type filter in fact occupies a position other than the :::
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most favourable position inside the vessel in which the axis of the filter is substantially parallel with the axis of the vessel.
An object of the present invention is to overcome or at least mitigate these disadvantages.
According to the present invention, there is provided a filter for placing in a folded condition into a part of the blood system and unfolding therein to retain blood clots, the filter comprising a plurality of resilient fingers which, in the unfolded condition, extend divergingly from a head to form a generally conical shape, each finger being provided at its distal end with a centring and bearing runner extending, in normal use, in the unfolded condition, substantially parallel to the substantially cylindrical wall produced by a generating line parallel with the axis of the said conical shape and describing as a locus the perimeter of the base of the conical shape, wherein the fingers and the runners comprise flexible wires, the fingers being arranged in pairs of two adjacent fingers having their respective distal ends joined by a piece of wire folded in the manner of a hairpin, the runners comprising the limbs of the hairpin wire, the ends of the hairpin connected to the said corresponding ends of the fingers being substantially located on the perimeter of the base of the conical shape.
Such a filter may have a certain degree of flexibility in order to facilitate positioning, with a degree of rigidity and a~ial stability which are sufficient to ensure that it holds well in the vein and provides high quality filtration.

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When the filter is positioned in a vein, it has a broad supporting area which decreases trauma owing to the contact pressure on the vein walls. Moreover, the centring and bearing runners are held firmly from the outset against the vein walls, forcing the filter to adopt a position such that its axis is substantially coextensive with the axis of the vein.
The preferred wire structure enables the fingers and their runners to be deformed in several directions, enabling the fingers to be grouped in a small space and facilitating fitting by means of fine insertion devices. Furthermore, combining the fingers in pairs prevents their becoming tangled.
In a preferred embodiment of the invention, the bight portion, at which the wire portions are folded in the manner of a hairpin, is directed towards the head of the cone.
In a further embodiment of the invention, the said fingers are arranged in pairs of two adjacent fingers each pair comprising a single wire folded on itself in the shape of a clip and held locally at the head.
Advantageously, the wire portions folded into the shape of a hairpin may define substantially triangular areas. This particular shape or "triangulating" of the wires enables the two ends of each wire to be moved together easily. In the folded position, the filter then occupies a small amount of space, the two ends of the wires extending substantially adjacent one another, along each other, the assembly of the wire bundle ` retaining all its flexibility without the risk of becoming tangled when the filter is released in the vein.

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- 21~0900 At their ends opposite those joined to the runners, the flexible wires constituting the fingers may be secured in a solid head of a generally ogival shape and having preshaped holes.
The filter may be provided with means for attaching the filter to the vein, more precisely anchorage hooks.
A more detailed description of the invention will now be given, by way of non-limiting example only, with reference to the accompanying drawings in which:
Figure 1 shows schematically in perspective a filter in accordance with the invention in its unfolded state;
Figure 2 shows schematically the filter implanted in a vessel;
Figure 3 is a detailed view of two adjacent fingers joined to one another;
Figure 4 shows the securing of the wires in a solid head, the left hand third of the Figure being in section; -Figure 5 shows a bottom view of Figure 4, substantially along the arrow V in this Figure;
Figures 6 and 7 show two successive stages of the formation of a hook;
Figure 8 shows the securing of a hook on the wire, the base of the hook being flattened about the said wire:
Figure 9 shows in section the securing of the hook substantially along the arrows B;
Figure lO shows a variant of the securing of the hook, the base of the hook being folded about the wire;

Figure 11 shows in section along the arrow C the variant of the securing of the hook; and Figures 12, 13 and 14 show three successive stages for positioning the filter according to the invention in a vessel.
With reference firstly to Figure 1, there is illustrated a filter 1 in the unfolded position comprising fingers 2, of which there are ten for example, which emerge from a head 3 and which can be unfolded substantially into a generally conical shape of which the opening perimeter is marked in dashed lines at 4. Each finger is provided at its free or distal end with a centring and bearing runner 5 which returns substantially behind the head 3;
that is, this runner 5 is directed from the end 2a of the fingers towards the closure side of the cone formed by the filter. More precisely, the runners 5 are directed such that they are substantially parallel with the wall of the cylinder, designated 6, generated by a generating line parallel with the axis 7 of the conical shape formed by the filter 1 when the generating line is moved such that it describes, as a locus, line 4.
The filter fingers comprise flexible wires 8. They may in particular comprise metal wires, for example of a suitable grade of stainless steel, such as that known as AFNOR K 13C20 N16 Fel5 for example, known in particular by the registered trade mark of "Phynox". The diameter of the wires may be between 2 and 4 tenths of a millimetre, for example 3 or 3.5 tenths of a millimetre.
These fingers are arranged in pairs of two adjacent fingers.
` Each pair of two adjacent fingers is connected by a wire part ~, :

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which is folded in the manner of a hairpin 9 and forms the said runners. As a result, the fingers are in the general shape of a clip 10, as illustrated in Figure 3. Advantageously, the filter comprises at least six of the above fingers connected to three wire portions folded in the manner of a hairpin and distributed in an angular manner so as to ensure that the filter has good axial stability.
A filter embodying the invention is positioned according to the conventional process which is facilitated by the flexibility of the filter.
Figure 2 illustrates a filter 1 implanted in the unfolded position inside a blood vessel 11, especially a vein, such that it can intercept any clots circulating therein, the direction of the blood flow being marked by the arrow 12. The runners 5 are held firmly against the inner wall of the vein thus enabling the filter to centre itself in the vein.
Figure 3 shows a detailed view of a clip 10 consisting of two adjacent fingers 2 joined by a wire portion folded in the form of a hairpin 9. Advantageously, this hairpin-like wire portion delimits a substantially triangular area 9a such that greater stability of the implanted filter is ensured.
Figures 4 and 5 show the connection of the ends of the wires at the location of the head 3.
As shown in Figure 4, the ends of the wires 13 forming the fingers opposite those ends joined to the runners are secured in a solid head. The ends of the wires are inserted into an equivalent number of holes 15 preformed in the head.

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Advantageously, the substantially ogival solid head 16 comprises a cylindrical bore 17 at its base end. The wires are secured in the head by means of a generally cylindrical part 18 of which the diameter and height are substantially equal to those of the bore 17 and which has recesses 19 parallel with the axis of rotation 20 of the part 18 and opening onto the outer surface of the part 18. These recesses 19 are distributed in an angular manner and the ends of the wire which are located therein are then secured by the inner wall 21 of the head as shown in Figure 5.
The so-called permanent filters which are inserted when there is a constant risk of the passage of clots and which thus remain in place for the duration of the patient's life are provided with attachment means in order to prevent any migration of the filter in the vessel.
Filters embodying the invention may be provided with attachment means of this type which are to penetrate the wall of the vessel slightly. In effect, at least some of their runners are provided with anchorage hooks.
With reference to Figures 6 and 7, the constitution and manufacturing process of these anchorage hooks will now be described.
The starting point is a thin plate made of metal, for example, from which the blank of a hook 22 is cut out, as shown in Figure 6, substantially in the shape of a T of which the staff is a tapered part 23.
The blank formed in this manner is subjected to a shaping operation as illustrated in Figure 7. Firstly, the tapered : ,.~. .
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portion is made substantially V-shaped as a result of being moved away from the plane of the blank. The bar 24 of the T-shape is likewise shaped by the folding of its two arms 24a until they are substantially parallel. Subsequently, the tapered portion 23 is sharpened such that its end forms a point 25.
Reference will now be made to Figures 8 to 11 for the description of the positioning of the hook on an arm of the wire.
Figures 8 and 9 show a first technique for securing hooks on the wires. The hook 22 placed on the wire 8 is secured as a result of the arms 24a of the bar 24 being flattened about the wire to grip opposite sides of the wire at points 26, as shown in Figure 8. As shown in Figure 9, which illustrates a view in section of Figure 8, the ends of arms 24a remain free and parallel.
Figures 10 and 11 show a second possible technique for securing the hooks. In accordance with Figure 10, the hook 22 is placed on the wire 8 and the two arms 24a then are folded around the wire 8.
Figure 11 shows a sectional view on the line C-C of Figure 10 illustrating the folding of the arms 24a whereby the ends are close to each other.
Figures 12, 13, 14 illustrate schematically a method of inserting a filter embodying the invention in a vessel.
The filter is positioned through an insertion tube 27 generally known in the art as a "Desilet".
In Figure 12, the filter 1 is pushed inside the tube 27 by means of a pusher 28. It will be noted that the filter, in the 2~009ao folded position, is positioned such that its head 3 emerges last, the tube 27 having been introduced against the flow of blood indicated by the arrow marked 29.
In Figure 13, the filter 1 appears emerging from the tube and already having a substantially conical shape.
Figure 14 shows the filter 1 a moment later. ~he fingers are completely unfolded and their runners 5 define a substantially cylindrical envelope which is substantially coaxial with the axis 30 of the vessel and bears against its walls ensuring that the filter centres itself in the vein.
The tube 27 can then be withdrawn via its access route.
The positioning described above corresponds to the fitting of a filter by the jugular route. If it is fitted via the femoral route, the filter is released into the vein in the opposite direction, head first, where once again the triangular fingers constituting the filter ensure that it is centred.
It is evident that the foregoing embodiment of the present invention is only described purely by way of non-limiting example and that any useful modification can be made thereto without departing from the scope of the invention as defined by the following claims. Thus, according to a variant, the filters described can be used as temporary filters and in this case they are not provided with anchorage hooks.
In accordance with a further variant, the said clips can all be formed from a single flexible wire suitably shaped and held substantially at points on the head.

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Claims

1. A filter suitable for placing in a folded condition into a part of the blood system and unfolding therein to retain blood clots, the filter comprising a plurality of resilient fingers which, in the unfolded condition, extend divergingly from a head to form a generally conical shape, each finger being provided at its distal end with a centring and bearing runner extending, in a normal position of use, in the unfolded condition, substantially parallel to the substantially cylindrical wall produced by a generating line parallel with the axis of the said conical shape and describing as a locus the perimeter of the base of the said conical shape, wherein the fingers and the runners comprise flexible wires, the fingers being arranged in pairs of two adjacent fingers having their respective distal ends joined by a piece of wire folded in the manner of a hairpin, the runners comprising the limbs of the hairpin wire, the ends of the hairpin connected to the said distal ends of the fingers being disposed substantially on the perimeter of the base of said conical shape.

2. A filter as defined in claim 1, wherein the bight portion of said wire pieces folded into the shape of a hairpin is directed towards the head of the conical shape.

3. A filter as defined in claim 2, wherein the said fingers of a pair of adjacent fingers comprise a single wire folded on itself in the shape of a clip and held locally at the head.

4. A filter as defined in claim 3, wherein the said clips are all formed from a single flexible wire suitably shaped and held substantially locally at the said head.

5. A filter as defined in claim 1, wherein the said pieces of wire folded into the shape of a hairpin define substantially triangular areas.

6. A filter as defined in claim 5, comprising at least six of the said fingers connected to three sections of wire folded into the shape of a hairpin and distributed angularly about the above-mentioned axis of the filter.

7. A filter as defined in claim 6, wherein the said flexible wires constituting the said fingers are each secured at their end opposite the end which joins the said runners, in preshaped holes of a solid head of generally ogival shape.

8. A filter as defined in claim 1, wherein at least some of the said runners are provided with anchorage hooks.

9. A filter as defined in claim 8, wherein the hooks comprise folded metal portions which are secured on the said runners.